Field of the Invention
The present invention relates to a honeycomb structure, and a manufacturing method of the honeycomb structure, and more particularly, it relates to a honeycomb structure which is capable of achieving uniformity of a flow rate of a fluid such as an exhaust gas to pass through the honeycomb structure, and a manufacturing method of the honeycomb structure.
Description of the Related Art
Heretofore, an exhaust gas emitted from an internal combustion engine such as a car engine includes toxic substances such as carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). Natural environments, human bodies and others are adversely affected, and hence the toxic substances cannot be discharged to the air as they are. To eliminate this problem, in a middle of an exhaust channel route of the exhaust gas, an exhaust gas purifying device to remove and purify the above toxic substances is usually provided.
As this exhaust gas purifying device, for example, a honeycomb catalytic body is used in which there is used, as a catalyst carrier, a honeycomb structure made of a porous ceramic material and having partition walls defining a plurality of cells to become through channels for a fluid (an exhaust gas), and a catalyst is loaded onto the partition walls of the honeycomb structure. Especially, in a case of purifying the exhaust gas emitted from a diesel engine, there is used a technology of selective catalytic reduction (SCR) to convert NOx into a nitrogen gas and water by use of ammonia (NH3) as a reducing agent, thereby enabling a treatment of NOx at a high purification efficiency.
A purifying treatment of NOx will further specifically be described. When passing the exhaust gas of the fluid from one end face (an inflow side) to the other end face (an emission side) of the honeycomb catalytic body, the exhaust gas including NOx is dispersed to pass through the respective cells. At this time, the catalyst loaded onto the partition walls comes in contact with the exhaust gas. Especially, the honeycomb catalytic body is a structure including a plurality of cells, and hence it is possible to broadly take an opportunity of contact between the exhaust gas and the catalyst and a contact area of the exhaust gas with the catalyst.
As a result, the above exhaust gas purifying device can exert a high NOx purifying performance. Here, as the catalyst for use, it is possible to select at least one from the group consisting of various metal catalysts such as a metal-substituted zeolite, vanadium, vanadia, titania, tungsten oxide, silver and alumina (e.g., see Patent Document 1).
Furthermore, for the purpose of achieving uniformity of a flow rate of a fluid such as the exhaust gas and eliminating unevenness of a treatment region of the fluid in a structure end face, there has been suggested manufacturing of a honeycomb structure in which a honeycomb body having a high-pressure loss is disposed in a region where the flow rate is high. On the other hand, a honeycomb body having a low pressure loss is disposed in a region where the flow rate is low, whereby respective regions of the structure end face have different cell structures (e.g., see Patent Document 2).
[Patent Document 1] JP-A-2009-154148
[Patent Document 2] JP-A-2003-025316